Liquid Crystal Display (LCD) devices have found increasing use in areas such as watches, calculators, computers and television screens. A typical LCD device is shown in U.S. Pat. No. 4,776,673, issued to S. Aoki et al. on Oct. 11, 1988. The typical LCD device comprises opposed transparent substrates of glass, or the like, which are spaced apart by a small distance and sealed along the edges to contain a liquid crystal material therebetween. A plurality of display electrodes and associated thin film transistors, for providing switching, are formed in a matrix on the inner surface of the first opposing transparent substrate. A transparent common electrode layer is formed on the second opposing transparent substrate to form a capacitor with each of the plurality of display electrodes of the matrix. Each display electrode and associated transistor form a "pixel" of the display matrix.
Scanned flat panel LCD devices, such as the LCD device shown in Aoki et al. and described above, also include data and select scanners to enable the pixels to form the display image. Such data and select scanners require power, high speed clock and data signals to properly operate the pixels of the optically active region. To provide such power, clock and data signals, distribution of power supply lines, high speed clock lines, and data lines are usually provided around the optically active region within the liquid crystal material area and between the two transparent substrates. Such lines can cover distances of up to approximately two meters to supply the necessary signals to data and select scanners for operating the optically active display region to provide a display image.
The problem is that even when lightly loaded, the intrinsic Resistance-Capacitance (RC) delay associated with conventional 1 micron thick aluminum signal and power lines is in some applications too high for routing more than a distance of 10 to 20 centimeters on an LCD plate or substrate. These sized lines are especially not suitable for routing the necessary high speed lines around the large plates or substrates needed for applications such as high definition television and computer work stations. Additionally, the conductor thickness cannot be increased significantly without increasing the liquid crystal spacing between the two opposed transparent substrates, and thereby degrading the optical performance of the display. Additionally, widening the conductors decreases the resistance but increases the capacitance with the transparent electrode formed on the opposite transparent substrate and, as a result, does not provide a solution to the problem.
It is desirable to have high speed signal and power supply bussing for an LCD device which can provide reasonably low resistance conductors and a reasonably low RC time constant so as not to degrade the optical performance of the display.